Atypical mycobacteria obtained from the sputa of 7 cases and from the urine of 1 case among 8 cases of tuberculosis under middle grade during last 8 months were examined.
The bacilli were acid-fast, and grew on the Qgawa's media forming yellow (4 cases), orange (3 cases) and white (1 case) colonies of S type. The boiling test as well-as Gram's stain were positive. They were fairly larger than tubercle bacilli, and grew well on the O. K's and Kirchner's media, but not on the routine media.
All cases were previously treated with antituberulotics for long period. The resistance to chemotherapeutics was over 10γ of SM in 6, over 10γ of INH in 5, over 10γ of PAS in 4 among 7 strains, and the natural resistance was 10γ of PZA, and 1-10γ of VM.
Pathogenity of the atypical mycobacteria for guinea pigs and hamsters was compared to that of H37Rv and Aoyama. B strains, and no pathogenity was found by intraperitoneal injection of 1.0 mg or less.
But, in the 4 cases out of the 6 which were sacrificed 14-100 days after the intraperitoneal injection (10 mg in guinea pigs and 3 mg in hamsters) the tubercle-like lesions were found in lung, liver, spleen, omentum and peritoneum. As for the histological-pictures of these lesions in some cases only tubercles with epitheloid cells, monocytes and small round cells were found, however, in other cases fresh Langhans giant cells and casseation were also found.
It was ascertained that the atypical mycobacteria were different from tubercle bacilli in their character of colonies and their resistance to chemotherapeutics, and although their pathogenity for experimental animals was slight, they gave tubercle-like lesions.
